The problem of providing a low inductance connection between a shielded cable and circuitry on a printed circuit board has been in existence for a long time. It is complicated when there is also a requirement that a chassis ground be isolated, from a DC standpoint, from the signal ground. This is accomplished in some prior art approaches by capacitively coupling the signal ground to chassis ground. One such example is found in a U.S. Pat. No. 4,827,378, issued May 1, 1989, to Rockwell International Corporation, and since assigned to the assignee of the present invention. The referenced patent, however, uses a spring to provide the contact between the shielded cable connector and the capacitor providing the connection to chassis ground. This point contact acts like a pigtail connection and introduces inductance into the circuit which raises the impedance and thus, reduces the ground shield effectiveness. The ground contact at only one or a few points surrounding the signal conductor allows the radiation of electromagnetic signals as well as the pickup of electromagnetic signals from nearby high frequency sources.
Another approach to solving the present problem utilizes an expensive coaxial connector where a high cost dielectric such as ceramic is used. While the connector performed reasonably well for the purposes for which it was designed, the connector was not designed to utilize compliant pin technology and the cost was prohibitive in most commercial applications.
The present invention utilizes printed circuit board material as dielectric and high capacitance can be obtained by using multilayers. Substantially continous circumferential contact between the connector and the capacitor can be obtained by proper methods of attaching the connector to the printed circuit board wherein there is substantially 360 degree contact between the connector and one layer of capacitive material. With proper design of plated-through holes and intermediate layers of conductive material in a multilayer printed circuit card, a cable connector may be produced which has the desired low inductance along with a relatively low cost and which still maintains EMC (electromagnetic compliance) standards.
It is therefore an object of the present invention to provide an improved shielded cable connector to printed circuit interface where it is desirable to have an isolated chassis ground and/or high standards of electromagnetic signal shielding.